There is a conversation going on here about consolidating constructive
and progressive buttons: https://phabricator.wikimedia.org/T110555
I want to find out if any of you have used these buttons in your
interface and have done any testing with your users to see if they
understand the difference between the two. Also, if you have used it
in other ways that has been helpful to your users, chime in!
Progressive (blue) conveys to the user that they are starting or
continuing a multi-step process.
Constructive (green) conveys to the user they are completing a single
or multi-step process. In most case Constructive color shows the user
what will happen. In others it is feedback that the action has
completed. For example, thanking a user, adding a page to a watch
Related discussion about button consolidation: